1. Field of the Invention
This invention relates to surgical procedures and, more particularly, to a position sensing system or a guidance system adapted to assist a surgeon in locating a predetermined position once a transmitter or receiver is surgically implanted.
2. Description of the Related Art
Localization wires have long been used to assist surgeons in identifying the position of certain tissue inside the human body. For example, localization wires are often implanted for the purpose of guiding a surgeon to a tumor or lesion for surgical excision.
In one known application of the localization wire, the distal tip of a hollow needle is inserted into body tissue and positioned so that the distal tip of the needle is immediately adjacent to the desired tissue or lesion. Next, the localization wire is inserted through the hollow needle until the distal tip of the wire is positioned in or immediately adjacent to the lesion. Finally, the needle is withdrawn, leaving the wire in the appropriate position. The needle and wire are typically positioned by a radiologist using conventional methods and equipment. Preferably, a barb or tine is formed at the end of the wire for holding the wire in position. Once the wire is properly positioned, the surgeon uses the wire as a guide for the biopsy or excision of the tissue adjacent the end of the wire. The surgeon can follow the wire to the lesion for excision. However, this procedure oftentimes creates more cicatricial tissue than is necessary. In an effort to minimize cicatrix formation, surgeons have adopted the technique of inserting the biopsy needle at a location remote from the localization wire.
It is known to provide enhancements on the wire and needle to assist the users in positioning the wire and needle and also identifying the depth of insertion of the wire, as seen in U.S. Pat. Nos. 5,158,084 and 5,490,521. Despite the known enhancements on the wire, it is still difficult for surgeons to accurately locate the distal tip of the positioned localization wire without causing excess trauma to the surrounding tissue.